Identification of coiled bodies in Brassica napus nuclei during embryogenesis and early germination

Nucleolus-associated bodies characterize interphase nuclei of many plant sp ecies. The recent demonstration that such bodies contain small nuclear ribo nucleoproteins as well as coilin clearly indicates that they belong to a la rger family of nuclear structures, known as coiled bodies, that have been i ntensively studied in a variety of animal cell types. In a previous work, w e have shown that coiled bodies were present in close association with the nucleolus in Zen mays dry seeds as well as during subsequent stages of germ ination. This study reveals that similar nuclear structures were also prese nt during Brassica napus embryogenesis starting at the torpedo stage and th at they were, likewise, generally located on the nucleolar surface. As in t he case of Z. mays, coiled bodies were observed in cells of dry seeds as we ll as in those of early germinating tissues. These bodies were labelled wit h monoclonal antibody K121, an antibody reacting with the unique 5'-termina l cap structure containing 2,2,7-trimethylguanosine that characterizes smal l nuclear RNAs. Owing to their intimate association with the nucleolus in a ll stages studied, the possibility is considered that, in these plant cells , coiled bodies are assembled on an organizer element located within this o rganelle.